【正文】 reach for a ci garette. Try som e deep breathi ng i nstead. Do som e rel axati on exerci ses every ti m e you feel stressed. Get hel p i f you need i t. Arrange to stop sm oki ng wi th a fri end so you can tal k about your probl em s, or joi n a stopsm oki ng group. If you feel desperate, you mi ght l ie to tal k to a doctor or chemi st about som ething to hel p you, li ke ni coti ne chewi ng gum. Kep tryi ng. Do not be di sappoi nted i f you have to try several tim es before you fi nal y stop sm oki ng. If you weaken and have a ci garette, do not feel asham ed. Just try agai n. You wi l succeed eventual y. H IV/AIDS。 that i s, the part of the body that fights di sease. You can have H IV i n your bl ood for a long tim e, but eventual y H IV wil l dam age your im mune system so m uch that your body can no l onger fi ght di sease. This stage of the il ness i s cal l ed AIDS. If you devel op AIDS, your chances of survi val are very sm al l. H IV i s spread through bl ood or the fl ui d that the body m akes duri ng sex. For a person to be e i nfected, bl ood or sexual fl ui d that cari es the virus, has to get i nsi de the body through broken ski n or by i njecti on. O ne day sci enti sts wi l fi nd a cure for H IV/AIDS. Until that happens, you need to protect yoursel f. H ere are som e thi ngs you can do to m ake sure you stay safe. If you i nject drugs: do not share your needl e with anyone el se. Bl ood from another person can stay on or i n the needl e. If a person has H IV and you use the sam e needl e, you coul d i nject the vi rus i nto your own bl od. do not share anythi ng else that a person has used whi l e i njecti ng drugs. Bl ood coul d have spi l t on i t. If you have sex wi th a m al e or a fem al e: use a condom. Thi s wi l prevent sexual fl ui d passing from one person to another. The fol owi ng statem ents are NOT true. A person cannot get H IV the fi rst tim e they have sex. WRO N G. If one sexual partner has H IV, the other partner coul d be e i nfected. You can tel l by l ooki ng at som eone whether or not they have H IV. WRO N G. Many peopl e carryi ng H IV l ook perfectl y heal thy. It i s only when the di sease has progresed to AIDS that a person begi ns to l ok si ck. Onl y hom osexual s get AIDS. WRON G. Anyone who has sex with a person i nfected wi th H IV/AIDS ri sks geti ng the vi rus. Wom en are sl i ghtl y m ore li kel y to be e i nfected than m en. If you hug, touch or ki ss som eone wi th AIDS or visi t them i n thei r hom e, you wi l get H IV/AIDS. WRO N G. You can onl y get the di sease from bl od or sexual fl ui d. Unfortunatel y, peopl e wi th H IV som etim es l ose thei r friends because of prejudi ce. Many peopl e are afrai d that they wi l get H IV/AIDS from those i nfected with H IV/AIDS. For the same reason, som e AIDS pati ents cannot fi nd anyone to l ok after them when they are sick. You can get H IV/AIDS from m osquitoes. WRON G. There i s no evi dence of thi s. Unit 4 TH E EARTH IS BECO MIN G WARMER BUT DO ES IT MATTER? Duri ng the 20th century the tem perature of the earth rose about one degree Fahrenhei t. That probabl y does not seem m uch to you or m e, but i t i s a rapi d i ncrease when pared to other natural changes. So how has thi s e about and does i t m ater? Earth Care?s Sophi e Armstrong expl ores these questi ons. There i s no doubt that the earth i s be ing warm er (see Graph 1) and that i s i t human acti vi ty that has caused thi s gl obal warmi ng rather than a random but natural phenom enon. Al l sci enti sts subscri be to the vi ew that the i ncrease i n the earth?s tem perature i s due to the burni ng of fossi l fuel s l i ke coal, natural gas and oi l to produce energy. Som e byproducts of thi s process are cal ed “greenhouse” gases, the m ost i m portant one of whi ch i s carbon di oxi de. Dr Jani ce Foster expl ai ns: “There is a natural phenom enon that sci enti sts cal l the ?greenhouse effect?. Thi s is when sm al am ounts of gases i n the atm osphere, l ike carbon di oxi de, m ethane and water vapor, trap heat from the sun and therefore warm the earth. Wi thout the ?greenhouse effect?, the earth woul d be about thi rtythree degrees Cel sius cool er than i t i s. So, we need those gases. The probl em begi ns when we add huge quanti ti es of extra carbon di oxi de i nto the atm osphere. It m eans that more heat energy tends to be trapped i n the atm osphere causing the gl obal tem perature to go up.” We know that the l evel s of carbon dioxi de have i ncreased greatl y over the l ast 100 to 150 years. It was a sci enti st cal ed Charles Keel ing, who m ade accurate m easurem ents of the amount of carbon di oxi de i n the atm osphere from 1957 to 1997. H e found that betwen these years the carbon di oxi de i n the atm osphere went up from around 315 parts to around 370 parts per mi li on (see Graph 2). Al sci enti sts accept this data. They al so agre that i t i s the burni ng of m ore and m ore fossil fuels that has resulted i n thi s increase in carbon di oxi de. So how hi gh wi l the tem perature i ncrease go? Dr Jani ce Foster says that over the next 100 years the am ount of warm i ng coul d be as l ow as 1 to 1. 5 degrees Cel si us, but i t coul d be as hi gh as 5 degrees. H owever, the attitudes of sci enti sts towards thi s ri se are pl etel y di fferent. O n the one hand, Dr Foster thi nks that the trend whi ch i ncreases the tem perature by 5 degrees woul d be a catastrophe. She says, “We can?t predi ct the clim ate wel enough to know what to expect, but i t coul d be very serious.” O thers who agree with her thi nk there m ay be a ri se of several m etres i n the sea l evel , or predi ct severe storms, fl ods, droughts, fam ines, the spread of diseases and the di sappearance of speci es. O n the other hand, there are those, li ke Gee H am bl ey, who are oposed to thi s vi ew